# File lib/prawn/font/ttf.rb, line 26
      def width_of(string, options={})
        scale = (options[:size] || size) / 1000.0
        if options[:kerning]
          kern(string).inject(0) do |s,r|
            if r.is_a?(Numeric)
              s - r
            else 
              r.inject(s) { |s2, u| s2 + character_width_by_code(u) }
            end
          end * scale
        else
          string.unpack("U*").inject(0) do |s,r|
            s + character_width_by_code(r)
          end * scale
        end
      end